The present invention relates to a chuck key and expecially to a chuck key for lathe chucks although the invention also relates to keys for devices intended to grip tools or workpieces during rotation.
A typical chuck key comprises a key shaft with a key-head provided with four lateral planar engagement surfaces, for detachable engagement with a corresponding swuare recess in the chuck.
In general such chuck keys have the drawback that if the lathe is accidentally started whilst the key is in the chuck they do not become disengaged and serious accidents may result. It is not unusual for the lathe operator to have forgotten to remove the key from the chuck before starting up the machine.
Attempts have already been made to solve this problem by means of relatively complicated constructions, such as key-ejectors consisting of a spring-loaded sleeve or peg arranged to eject the key when the machine is started. However, such ejectors lead to a clumsy or complex chuck or key construction and the key is therefore difficult to manipulate since it requires a considerable force to insert it into the engagement position in the chuck. Because of their complicated design, such key-ejectors are also expensive to manufacture.